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Wednesday, October 15, 2008

The last issue of maxxTORQUE Lube Notes explained the regimes of lubrication including Hydrodynamic Lubrication, Boundary Lubrication and Elastohydrodynamic Lubrication. As promised, I will now talk about the formulation of motor oils and why we put all those additives in our oil. Before we get into the formulations of the motor oils, we better take a look at the functions of motor oil. If we understand what oil is doing, then we can better understand why we choose certain base stocks and additives.

Motor oil must perform the following functions:

Lubricate engine parts in order to prevent wear

Reduce friction and improve fuel economy

Maintain clean engine components

Prevent rust and corrosion

Minimize engine deposits

Provide engine cooling

Aid in engine starting

Provide ring seal for better combustion pressure

Each of these functions is vital to optimum performance as well as to the durability of the internal combustion engine. Motor oils are complex lubricating fluids carefully formulated to perform all of these functions.

Grandpa used to lecture me about the importance of draining the water separator on his farm’s diesel tractor. This man, who wouldn’t hesitate to fix things with haywire or binder twine was, however, a purist when it came to maintenance. Experience had taught him that draining the water separator could mean the difference between a well performing engine and one with problems – or one that didn’t run at all.

The investment required to properly maintain the fuel system meant avoiding the corrosion and scoring caused by water when it runs amok in the fine-tolerance components of a diesel engine.

Duramax engines are significantly more sophisticated than Grandpa’s tractor. One might think that these more sophisticated engines can look after themselves a little better. In a sense that is true: today, we have more feedback than ever coming from our engines. But to think that these engines can handle not being maintained as well as their less sophisticated forerunners is far from the truth. In fact, just the opposite: today’s fuel injectors and other components require much higher tolerances. Consider that a typical conventional diesel fuel system prior to the DMax operated at fuel pressures of 1,200 to 1,500 PSI. Then compare those numbers to the original LB7 fuel injector that operated in the range of 4,500 to 23,200 PSI!

In Direct Oil Cooling – Part One, we discussed indirect and direct cooling methods and we examined oil’s new role as a coolant, rather than a mere lubricant, with new technologies such as under-piston oil squirting shifting more – up to 50% more – of the turbo diesel’s total cooling burden to the oil. We observed worst-case oil temperatures exceeding 360ºF, causing oil pressure to plummet and rendering oil, as a lubricant, virtually useless. In Part Two, we’ll look at the science behind indirect and direct oil cooling and discover why direct cooling, properly engineered, offers the only solution that can control:

Oil temperature,

Viscosity, and

Flow rate

to design specification limits under those same high load/high RPM conditions; and, substantially expand the overall capacity of the cooling system. In doing so, we will discover a host of benefits that can be realized only by directly cooling your oil.